12.04 home encrypted and I have written down encryption passphrase. How to reset login password?

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I set up a friend with 12.04 and he forgot his password. I encrypted his home directory and I have written down the encryption passphrase during the first boot. If he changed his password after I wrote down the encryption passphrase during the first boot is this original encryption passphrase of any use? What should I do to reset or recover his password and keep everything accessible and functionally intact with the encrypted home directory?
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Stories similar to 12.04 home encrypted and I have written down encryption passphrase. How to reset login password?

On 12.04 LTS x64, I changed my user password via the User Accnts tool. After that I was unable to login again with my new password since my home directory is encrypted and the above-described bug does not allow decryption of the home directory with the new login password. The passphrase to decrypt the home directory is saved in a folder on my encrypted home directory.